Energy Conversion in Bull Sperm Flagella

With the use of a specially developed incubation chamber the rates of motility, respiration, and fructolysis were measured simultaneously on semen samples. By inhibiting the respiration with antimycin A, and/or the fructolysis with 2-deoxyglucose, the rates of each of the two ATP-producing pathways could be reduced independently. In this way the ratio of the amount of free energy produced by respiration and by fructolysis could be varied at will from 1 to 0. In uninhibited preparations approximately 75% of the free energy derives from respiration, and 25% from fructolysis. By the use of the absolute rates of respiration, fructolysis, and motility, the efficiency of the conversion of free energy into hydrodynamic work was calculated. After correction for the decay of the preparation during the experiment, this conversion efficiency was found to be 30–45% lower for free energy from respiration than for free energy from fructolysis. The difference in distribution of the enzymes for fructolysis and respiration over the flagellum was ruled out as the cause of the efficiency difference. The respiration could be 70% inhibited by oligomycin. It is concluded that approximately one-third of the free energy from respiration is used for maintenance of the mitochondria.     

Diameter Oscillation of Axonemes in Sea-Urchin Sperm Flagella

The 9 + 2 configuration of axonemes is one of the most conserved structures of eukaryotic organelles. Evidence so far has confirmed that bending of cilia and flagella is the result of active sliding of microtubules induced by dynein arms. If the conformational change of dynein motors, which would be a key step of force generation, is occurring in a three-dimensional manner, we can easily expect that the microtubule sliding should contain some transverse component, i.e., a motion in a direction at a right angle to the longitudinal axis of axonemes. Using a modified technique of atomic force microscopy, we found such transverse motion is actually occurring in an oscillatory manner when the axonemes of sea-urchin sperm flagella were adhered onto glass substrates. The motion was adenosine triphosphate-dependent and the observed frequency of oscillation was similar to that of oscillatory sliding of microtubules that had been shown to reflect the physiological activity of dynein arms (S. Kamimura and R. Kamiya. 1989. Nature. 340:476–478; 1992. J. Cell Biol. 116:1443–1454). Maximal amplitude of the diameter oscillation was around 10 nm, which was within a range of morphological change observed with electron microscopy (F. D. Warner. 1978. J. Cell Biol. 77:R19–R26; N. C. Zanetti, D. R. Mitchell, and F. D. Warner. 1979. J. Cell Biol. 80:573–588).     

Branchial Cilia and Sperm Flagella Recruit Distinct Axonemal Components

Eukaryotic cilia and flagella have highly conserved 9 + 2 structures. They are functionally diverged to play cell-type-specific roles even in a multicellular organism. Although their structural components are therefore believed to be common, few studies have investigated the molecular diversity of the protein components of the cilia and flagella in a single organism. Here we carried out a proteomic analysis and compared protein components between branchial cilia and sperm flagella in a marine invertebrate chordate, Ciona intestinalis. Distinct feature of protein recruitment in branchial cilia and sperm flagella has been clarified; (1) Isoforms of α- and β-tubulins as well as those of actins are distinctly used in branchial cilia or sperm flagella. (2) Structural components, such as dynein docking complex, tektins and an outer dense fiber protein, are used differently by the cilia and flagella. (3) Sperm flagella are specialized for the cAMP- and Ca²⁺-dependent regulation of outer arm dynein and for energy metabolism by glycolytic enzymes. Our present study clearly demonstrates that flagellar or ciliary proteins are properly recruited according to their function and stability, despite their apparent structural resemblance and conservation.     

The Comparative Ultrastructure of Sperm Flagella Central Sheath in Clitellata Reveals a New Autapomorphy of the Group

A comparative ultrastructural analysis of sperm tails of the hirudinean Hirudo medicinalis the branchiobdellid Branchiobdella pentodonta , and various microdrile oligochaetes ( Pananais frici, Paranais lioralis, Monopylephorus rubroniveus, Enchytraeus sp. and Bythonomus lemani has revealed a common modification of the primitive axonemal structure. A prominent central sheath embeds the two central tubules of the flagellum for a tract of variable length in the different species. The structure of radial links and link heads appears also modified: link heads, which are three for each radial link, are disposed in rows. Adjacent link heads arc also transversely connected to each other. The absence of these peculiar modifications in megadriles is interpreted as a secondary phenomenon. Since no homologous modification of the sperm tails is present in other spermatozoa, the prominent central sheath and radial links here described in three of the four taxa belonging to the Clitellata is considered a new autapomorphy for the whole group.     

The Flagella of Pseudomonas solanacearum

Summary: Electron microscopic examination of 5 strains of Pseudomonas solanacearum , including the proposed neotype, NCPPB 325, showed that the cells of these organisms possess polar flagella.     

A Sperm Midpiece Defect in a Hereford Bull with Variable Semen Quality and Freezability

A midpiece sperm defect with a frequency of 25-35% in ejaculates obtained from a Hereford bull with a 60 d non-retum rate of 76.4% after careful pre- and postfreeze semen selection was studied in light microscope and by transmission electron microscopy. The defect consisted in a folding and coiling of the distal midpiece characterized by disorganization and irregularity of mitochondria surrounding the axial fiber bundle, combined with retraction of doublet fibers and dislocation and fracturing of these elements and the corresponding dense fibers. Based on examination of the sper- matogenic epithelium it was concluded that the alterations in the axial fiber bundle were secondary to those in the mitochondrial sheath. The abnormality appeared to be related to the “Dag-like” defect earlier observed in different breeds.     

Radiation Damage to Bull Sperm Motility. II: Proton Irradiation and Respiration Measurements

Diluted bull semen samples were bombarded with a 24 Mev proton beam. Dose response curves for the fraction of cells which survived the bombardment and for the average velocity of the surviving cells were measured. Target theory indicated a cross section of the sensitive volume of 2.1 × 10^-10 cm². Respiration measurements showed that the oxidative phosphorylation in the sperm remained coupled after the bombardments. The efficiency with which free energy from ATP hydrolysis was converted into mechanical work by the sperm was found to decrease after proton bombardment. The half-value dose for this effect was two and a half times higher than the half-value dose for motility damage. These respiration measurements indicate that the damage due to the bombardment is not to the metabolic system or to the contractile system in the sperm flagellum, but to a control system for the motility. The results of the target theory shows that this control system is localized in a small element of approximately 1600 A diameter. The centriole is tentatively proposed as being this control element.     

BIREFRINGENCE OF SPERMATOZOA : I. Birefringence Melting of Squid, Bull, and Human Sperm Nucleoprotein

In experiments designed to determine the thermal stability and bonding strength of a natural nucleoprotein structure, the loss of birefringence as a function of time and temperature was investigated for both mammalian and nonmammalian sperm nuclei. At a constant temperature, this reaction was found to be first order for both types over a range of temperatures. The methods of chemical kinetics applied to results of these reactions, called birefringence melting reactions, produced values for the enthalpy and entropy of activation in the reactions, which gave some indication of the strength of binding in the nucleoprotein structure; and these results, plus those on the influence of chemicals on the structure, were consistent with the molecular structures which have been proposed by others for the nucleoprotein complex of sperm nuclei. For both bull and human sperm in ethylene glycol, the rate-limiting step in the melting reactions appeared to be the breakage of disulfide bonds. For squid sperm in ethylene glycol, and bull or squid sperm in ethylene glycol plus β-mercaptoethanol, the identity of this step was more ambiguous, but a possibility consistent with these and other results would be a cooperative breakage of ionic bonds.     

Basal Organelles of Bacterial Flagella

Liberated by enzymatic lysis of the cells, the flagella of Rhodospirillum rubrum, R. molischianum, and R. fulvum all have a similar structure. The hook at the base of the flagellum is connected by a short, narrow collar to a paired disc in the basal organelle. This paired disc is in turn connected to a second paired disc. The disposition of flagella to which fragments of the cell membrane still adhere suggests that the narrow collar at the base of the hook traverses both the wall and the membrane, and that the upper pair of discs in the basal organelle lies just beneath the surface of the membrane.     

A Method for the Staining of Bacterial Flagella

A modification of the Loeffler method of staining bacterial flagella is proposed. The chief points of the modification are: The cultures are inoculated into distilled water after two successive daily transfers on agar slants, and the distilled water cultures are incubated at optimum temperature for from 48 to 72 hours. The mordant (tannic acid, ferrous sulphate, basic fuchsin) is allowed to stand 18 to 24 hours before use, and then cleared by centrifuging or filtering. An anilin water fuchsin is used as a stain. No heat is used for either mordanting or staining; but both mordant and stain are allowed to act on the preparation for 15 minutes. The writer finds the method admirably adapted for use in class work, where nearly 100 per cent success has been obtained except in the case of some three or four species of bacteria that are especially difficult to stain.